Mounting turret for elevation/azimuth antenna

ABSTRACT

A mounting turret for an elevation/azimuth antenna of the general type disclosed in U.S. Pat. application Ser. No. 750,444, filed Aug. 5, 1968 in the name of Robert D. Hall, one of the coinventors of the present invention, and assigned to the assignee of the present invention, is supported for rotative adjustment about an azimuth axis by wheels, which are mounted on the turret for rolling movement around an annular track mounted in a horizontal plane with its axis substantially coincident with a selected azimuth axis. A bull gear for rotatively driving the turret is fixedly mounted on the base coaxially with the annular/track, and spaced radially inwardly therefrom. A pair of power driven pinions mounted on the turret are in mesh with the bull gear for rotatively adjusting the turret. For maintaining the turret with its axis coincident with the selected azimuth axis, a bearing ring is mounted on the base with its axis exactly coincident with the azimuth axis, and a plurality of bearing pads, mounted on the turret are in bearing relation with the bearing ring. Holddown means for countering tilting moments imposed on the turret by the weight of an antenna mounted on the turret comprise a plurality of holddown wheels on the turret and in preloaded rolling engagement with the under side of an exposed marginal portion of the annular track.

United States Patent [72] Inventors Robert Dale Hall La Mesa; Salvatore A. Rocci, El Cajon, both of Calif. [21] Appl. No. 15,354 [22] Filed Mar. 2, 1970 [45] Patented Dec. 28, 1971 [73] Assignee Rohr Corporation Chula Vista, Calif.

[54] MOUNTING TURRET FOR ELEVATION/AZIMUTH Primary ExaminerMartin P. Schwadron Assistant Examiner-Frank Susko Attorney-George E. Pearson ABSTRACT: A mounting turret for an elevation/azimuth antenna of the general type disclosed in US. Pat. application Ser. No. 750,444, filed Aug. 5, 1968 in the name of Robert D. Hall, one of the coinventors of the present invention, and assigned to the assignee of the present invention, is supported for rotative adjustment about an azimuth axis by wheels, which are mounted on the turret for rolling movement around an annular track mounted in a horizontal plane with its axis substantially coincident with a selected azimuth axis. A bull gear for rotatively driving the turret is fixedly mounted on the base coaxially with the annular/track, and spaced radially inwardly therefrom, A pair of power driven pinions mounted on the turret are in mesh with the bull gear for rotatively adjusting the turret. For maintaining the turret with its axis coincident with the selected azimuth axis, a bearing ring is mounted on the base with its axis exactly coincident with the azimuth axis, and a plurality of bearing pads, mounted on the turret are in bearing relation with the bearing ring. Holddown means for countering tilting moments imposed on the turret by the weight of an antenna mounted on the turret comprise a plurality of holddown wheels on the turret and in preloaded rolling engagement with the under side of an exposed marginal portion of the annular track.

PATENTEU 05828197! 3.630.585

' SHEET, 1 OF 3 FIG1 INVENTOR. ROBERT D. HALL BY SALVATOREA. ROCCI a-W ATTORNEY PATENTEU UEBZ 8 I97! SHEET 2 BF 3 INVENTOR. ROBERT D. HALL A: y SALVATORE A. ROCCI ATTORNEY PATENTEU DEB28|97| v 3,630,5 5

SHEET 3 0F 3 FIG. 2-

INVENTOR ROBERT D. HALL Y SALVATORE A. ROCCI ATTORNEY MOUNTING TURRET FOR ELEVATION/AZIMUTII ANTENNA BACKGROUND OF THE INVENTION Large, reflector type antennae of the type employed in locating and tracking satellites, missiles, stars and other objects in space usually comprise a large, bowl-shaped reflector mounted for independent movement about two axes, one of which, the azimuth axis, is vertical, and the other, the elevation axis, is horizontal. Since the object in space toward which the antenna is directed may be hundreds of thousands, millions or even billions of miles away, it is obvious that the more accurately the antenna can be held and directed, the more satisfactory will be the results.

Previously mentioned patent application Ser. No. 750,444 shows such an antenna wherein an antenna support turret is mounted for limited rotative adjustment about a vertical azimuth axis, and an antenna bowl is mounted on the turret for elevational adjustment about a horizontal axis.

The antenna mounting and support means disclosed in said patent application are in many ways highly satisfactory, and superior to other known attempts to provide highly accurate support and control means for such a heavy, cumbersome, and usually off-balance structure, which is exposed to the elements, but the turret portion of said structure, and of other prior antennae of a similar nature, are difficult and expensive to manufacture and erect, and to maintain in the highly accurate condition which is essential to their successful use.

PURPOSE OF INVENTION The primary objective of this invention is to provide smooth, simple, powerful, highly accurate mounting and azimuth control means for an antenna of the general type disclosed in said Hall, patent application Ser. No. 750,444 referred to previously herein.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objective and advantages of the invention will be apparent from the following description and the accompanying drawings, wherein:

FIG. I is a plan view of an antenna rotor embodying the invention and its mounting structure.

FIG. 2 is an enlarged, fragmentary, sectional view taken along line 22 ofFIG. 1.

FIG. 3 is a further enlarged, fragmentary, top plan view looking in the direction of the arrows 3-3 of FIG. 2, but reversed, end for end.

FIG. 4 is a sectional view taken along line 44 of FIG. 3.

FIG. 5 is an enlarged, fragmentary, sectional view taken along line 55 ofFIG. ll.

FIG. 6 is a further enlarged, fragmentary sectional view taken along line 6-6 of FIG. 1.

FIG. 6 is a still further enlarged, sectional view showing the axial adjustment means for the inner end of each support wheel spindle.

DETAILED DESCRIPTION Referring to the drawings in detail, a pedestal base I0 of suitable material, for example, reinforced concrete, is erected on a building site selected for the antenna, the base I0 having an integral, annular track support portion II formed thereon with its axis substantially coincident with a selected azimuth axis I2, see FIGS. 1 and 2, which latter axis is also coincident with the axis of an upright tube 13 embodied in the base 10. The upper surface of the annular track support portion I1 is substantially flat and level, and an annular rotor support track 14 of suitable material, for example, machined forged steel, is mounted coaxially on the track support portion 11. The track I4 is supported on and leveled by, nuts 15, see FIGS. 2 and 6, which are screwed onto threaded rods 17 embedded in the base, and is retained thereon by holddown nuts 18. After leveling, the track I4 is more fully supported throughout its length by suitable bedding material I9, such as a grout mixture, interposed between the track and the base. The radially inward edge portion 140, see FIGS. 2 and 6, of the annular track I4 projects inwardly beyond the bedding l9 and the annular track support portion II to provide a track for holddown rollers to be described later herein.

An annular channel 20, coaxial with, and radially inwardly of the annular track support portion II, is formed in the top of the base I0, and on the inner rim of this channel an annular bull gear 21 is mounted with the teeth thereof directed radially outwardly. This bull gear 21 is carefully leveled, centered on the azimuth axis I2, and secured to the base I0, in the same general manner as that described previously herein for the track I4.

Spaced radially inwardly from the bull gear 21, and offset upwardly therefrom by annular steps 22 and 23, see FIG. 2, formed in the base it), is a bearing ring 24 with its axis exactly coincident with the selected azimuth axis I2. The bearing ring 24, which maintains a rotary turret 25 centered on the azimuth axis 12, is mounted in an angular, annular seat formed by the top surface of the annular step 23 and an annular riser face 27, as best shown in FIGS. 2, 3 and 4. The bearing ring 24 is supported on, and leveled by, nuts 28, screwed onto threaded rods 29 embedded in the base 10. The rods 29 extend through oversize holes provided therefor in the bearing ring 24.

After leveling, the bearing ring 24 is carefully centered on the azimuth axis 12, see FIGS. 1 and 2, by capscrews 30, see FIGS. 2, 3 and 4, screwed into radially extending, threaded holes provided at spaced intervals about the radially extending, threaded holes provided at spaced intervals about the radially inward face of the bearing ring 24, and axially aligned with the disclike heads of inserts 31 embedded in the riser face 27. By axially adjusting the capscrews 30, the heads of selected ones thereof are brought to bear against the heads of their respective inserts 31 to bring the axis of the bearing ring 24 into exact coincidence with the selected azimuth axis 12, after which the space between the bearing ring and the base 10 is filled with suitable bedding material 36.

The rotary turret 25 comprises a turret frame 32 of suitable material, such as, for example, steel beams arranged in the form of an isosceles triangle, with the angle defined by the even legs 33 and 34 thereof located on the opposite side of the turret frame 32 from that toward which the usual antenna bowl, not shown, swings in moving its focal axis from zenith toward the horizon.

Three angle frames 35a, 35b and 350, all of which are generally similar to each other, are mounted one at each angle of the triangular turret frame 32. Each angle frame 35, see FIGS. 2 and 5, is a strong weldment comprising a top plate 37 coextensive with, and welded to the turret side frame members forming the angle in which the angle frame is mounted, and a depending box structure comprising two similar sideplates 38, a radially outward end plate 39, an upright web 40, a bottom plate M, and a lower mounting plate 42. The latter plate, together with the sideplates 38, are also welded to the turret side frame members defining the angle in which the angle frame is mounted.

A turret support wheel 43 is mounted in each angle frame 35, each support wheel 43 being journaled on a suitable hear ing 44, see FIGS. 2 and 5, on a wheel spindle 47. Each wheel spindle 47 is mounted in a conventional, swivel-type support ring 46 anchored in an opening provided therefor in its associated apex frame outer end plate 39. The support ring 46 may be similar to that shown in Hall, application Ser. No. 750,444 referred to previously herein.

The inner end of each spindle 47 is of reduced diameter, and is fitted into a recess defined by an annular rim 48, see FIG. 7, on a wheel spindle mounting plate 49 secured in adjusted position on the radially inward side of each apex frame web 40. Each annular rim 48 is inserted in a slightly oversize hole, see FIG. 7, provided therefor in the web 40.

Each wheel spindle mounting plate 49 is secured in adjusted position to its respective web 40 by capscrews 50, best shown in FIG. 7, which are fitted with washers and inserted through oversize holes provided therefor in the spindle mounting plate 49. The capscrews 50 are screwed into threaded holes provided therefor in the web 40 and are drawn down tight when their associated mounting plate 49 is in properly adjusted position. After the capscrews 50 are thus tightened, a spacer block 51 is fitted between the lower edge of the spindle mounting plate 49 and the apex frame bottom plate 41 to prevent downward displacement of the spindle-mounting plate under the stresses imposed by the weight of the turret 25 with an antenna, not shown, mounted thereon.

It is important for smooth and accurate operation of the turret 25 that each turret support wheel 43 be mounted with its axis of rotation disposed in a radial plane from the azimuth axis 12. Also, in order to prevent relative slippage between the turret support wheels 43 and the track 14, the periphery of each wheel 43 is in the form of a truncated cone, with the circumference of its radially inward edge sufficiently smaller than that of its radially outward edge so that upon each rotation of the wheel 43, the developed circumference of each of said wheel edges will move through the same circumferential angle of the track 14.

For axially adjusting each support wheel 43 to its proper radial distance from the azimuth axis 12, a capscrew 52, see FIG. 7, is screwed through a threaded hole provided in the mounting plate 49 and bears against the radially inward end of its associated wheel spindle 47. Three anchoring screws 53, each with a runner nut 54 thereon, are also inserted through slightly oversize holes provided in the spindle-mounting plate 49 and are screwed into threaded holes provided in the inner end of the wheel spindle 47.

Screwing the screw 52 into its threaded hole in the mounting plate 49 with the runner nuts 54 on the other screws 53 freed, moves the wheel spindle 47 axially outwardly away from the azimuth axis 12, while reversing this procedure draws the spindle 47 inwardly. After the axial and angular positions of each support wheel spindle 47 have been adjusted, the screws 50 and runner nuts 54 are drawn down snugly to anchor the parts in adjusted position.

Four similar holddown roller assemblies 55, see FIGS. 1 and and 6, are provided on the angle frame 35 located in the angle defined by the equal turret frame side members 33 and 34. Each holddown roller assembly 55 comprises a boxlike weldment 57, see FIGS. 5 and 6, firmly secured, as by bolts 58, one to each side of each sideplate 38 of the angle frame 35c.

A clevis 59 is screwed onto the lower end of an upright stud 60 inserted through a hole in the bottom plate 61 of the weldment 57. The stud 60 is also inserted through slightly oversize holes provided in a pair of support plates 62 and 63 mounted on the weldment bottom plate 61, a sheet 64 of slightly resiliently compressible material being interposed between the plates 62 and 63 to provide for a slight degree of resilient adjustment if required. This interposed element 64 may be offelt impregnated with a suitable elastomer, or it may be of the product known as Fabreeka. The stud 60 is anchored in axially adjusted position in the clevis 59 by a locknut 65.

A rocker beam 67 is mounted for rocking movement in each clevis 59. The outer end of each rocker beam 67 is turned and a holddown roller 56 is journaled thereon on a suitable bearing 56a, see FIG. 6. An integral web 70 extends along the underside of each rocker beam 67 for adding strength and rigidity thereto, and an integral thrust block 71 is provided on the upper side of the opposite end of each rocker beam 67 from that upon which the holddown roller 56 isjournaled. A thrust screw 72 is inserted through a slightly oversized hole in each weldment bottom plate 61 into endwise engagement with its associated thrust block 71, and is adjusted axially by nuts 73 and 74 and a locknut 75 to urge its holddown roller 56 upwardly into desired preloaded engagement with the underside of the inwardly extending flange portion 140 of the rotor support track 14.

For adjusting each rocker beam 67 about its supporting stud 60 as an axis to bring the axis of the holddown roller 56 and roller bearing 56a mounted on the rocker beam within a radial plane from the azimuth axis 12, a pair of downwardly open, fixed yokes 77 and 78 are welded to extend downwardly from the underside of the weldment bottom plate 61 to span the rocker beam 67, two of said yokes being provided for each supporting stud 60. Each of the fixed yokes 77 and 78 comprises a short length of I-beam material with the lower portion of the web 79 thereof cutaway. A reinforcing plate 80, see FIG. 6, is welded externally onto each side of the lower end portion ofeach of said yokes 77 and 78, and a pair of adjusting screws 81, each with a usual locknut screwed thereon, are screwed into threaded holes provided in the reinforcing plates 80 to have bearing engagement with opposite sides of their associated rocker beam 67. The screws 81 are axially adjusted withjust sufficient clearance to permit free rocking movement of the rocker beam.

For rotatively driving the turret 25 about the azimuth axis 12, two similar, but reversed power drive mechanisms 82 and 83, see FIG. 1, are mounted on the third turret frame side member 84. Each drive mechanism 82 and 83 comprises a power source, which preferably is a reversible electric motor 85, operably connected through a conventional speed-reduction mechanism 87 to a drive pinion 88, the latter being in mesh with the bull gear 21. The motors are driven synchronously be a suitable source of electric current through conventional control mechanism, not shown, so as to rotate both pinions 88 synchronously at a selected speed and in a selected direction. Suitable rotor-braking or locking mechanism may be provided if desired, for example, that shown in Hall patent application Ser. No. 750,444 referred to previously herein.

To maintain the turret 25 properly centered on the azimuth axis 12 during operation, three box-beam centering arms 89, 90 and 91, are fixedly mounted, one on each of the three angle frames 35a, 35b and 35c, to extend inwardly toward the bearing ring 24 along radii from the azimuth axis 12.

A bearing pad unit 92, best-shown in FIGS. 3 and 4, is mounted on the radially inward end of each of the centering arms 89, 90 and 91. Each bearing pad unit 92 comprises a base portion 93 and a bearing pad assembly 94 mounted for swivel movement thereon. Each bearing pad assembly 94 comprises a pad-mounting portion 95 fitted for swivel movement into the base portion 93, and a bearing pad 96 of suitable low friction material, for example, oil-impregnated, sintered bronze, mounted thereon. The bearing face of each bearing pad 96 is curved concavely to conform to the radially outward face of the bearing ring 24 along which it rides.

The centering arms 89, 90 and 91 are of such length that when the turret 25 is properly centered relative to the azimuth axis 12, the inner ends of said arms are spaced substantially equally from the bearing ring 25 by a distance slightly greater, for example, V4 inch greater, than the overall length of the bearing pad unit 92 to be mounted therebetween. For mounting the bearing pad units 92 on their respective centering arms, each bearing pad unit is mounted, as best shown in FIGS. 3 and 4, in registering relation with the inner end of its associated centering arm. Equal forces are applied between the arms 89, 90 and 91 and their respective bearing pad units 92, as by screws 97, which are screwed into threaded openings provided in the end plates 98 of the centering arms 89,90 and 91, care being exercised to maintain the turret 25 centered on the azimuth axis 12. Suitable bedding material such as, for example, activated epoxy resin, is poured in to fill the space 100 between each radial arm and its respective bearing pad unit 92 and allowed to harden therein. The bottom and sides of each space 100 may be dammed off before pouring by means of suitable material, such as adhesive tape, if a liquid bedding compound is used.

ERECTION AND OPERATION The pedestal base 14) as shown in FIGS. ii and 2 is constructed in a conventional or desired manner. The annular track 14, bull ring 21 and bearing ring 24 preferably are machined from forgings as integral units. The track and bull ring in the case of large installations or remote building sites, may be cut up into segments of desired size for convenience in handling and shipping and reassembled at the building site,

but the bearing ring 24 preferably remains an integral unit.

All three annular members 14, 21, and 24, are mounted on the base as described previously herein, the former two being leveled by means of their respective supporting nuts such as the track support nuts 15, and stabilized by their holddown nuts 18 and bedding material 19. The bearing ring 24, in addition to being leveled in a similar manner, is also carefully centered by means of the radially projecting capscrews 30 to bring its axis into exact coincident with the selected azimuth axis 12.

The turret is mounted on the annular track 14 and is carefully centered relative to the azimuth axis 12 by means of the radial arms 89, 90 and 91 and their bearing pad units 92 and by adjusting screws 97, see F I68. 3 and 4, and the spaces 100 are filled with a suitable bedding material.

Upon loosening the screws 50, the support wheel spindles 47 are adjusted angularly in their respective swivel support rings 46, as explained previously herein, so that the axis of rotation of each turret support wheel 43 lies not only within a radial plane from the azimuth axis 12, but also at such tilt angle as to bring the line of tangency at the bottom of the wheel into full contact with the annular track 14. The screws 50 are then again drawn down tight and a block 51 is fitted beneath each spindle-mounting plate 49.

The support wheel spindles 47 are also adjusted axially by means of the screws 52 and 53 so that the support wheels are at required equal distances from the azimuth axis 12.

The rocker beams 67 are adjusted by means of the screws 81 in the fixed yoltes 77 and 78, see FIGS. 5 and 6, to position the axes of their respective holddown rollers 56 in radial planes from the azimuth axis 12. The rocker beams 67 also are adjusted by means of the nuts on the yoke-mounting studs 60, and those on the thrust screws 72, to have full, tangent engagement within the underside of the track flange 14a, and with selected preloading stress.

The motor drive mechanisms 82 and 83 are adjusted, if necessary, for example by shimming, to bring their respective rotor drive pinions 88 into proper mesh with the bull gear 21.

Any desired type of antenna bowl, not shown, or other structure may be provided on the turret 25, for example, an antenna bowl such as that disclosed in the Hall, patent appli cation Ser. No. 750,444, referred to previously herein.

The invention provides a strong, simple, rigid, highly accurate antenna-mounting structure, and one which is capable of being readily transported and erected in remote areas with relatively unskilled labor, thereby overcoming problems frequently encountered in the field. It tends to retain its accuracy over long periods of time with minimum maintenance, but is easily adjusted if required.

Having disclosed a preferred form of the invention, I claim:

1. An antenna support structure comprising,

a base having a selected azimuth axis,

an annular turret support track mounted in leveled condition on the base with its axis substantially coincident with the selected azimuth axis,

a bearing ring of different diameter from the track mounted on the base substantially coaxially with, and in radially spaced relation to the track,

means for adjusting the bearing ring to bring its axis into exact coincidence with the selected azimuth axis,

an antenna support turret mounted for rotative adjustment on the track, said turret comprising a turret frame mounted substantially coaxially with the track,

a plurality of at least three turret support wheels mounted on the turret frame and riding circumferentially along the annular track,

a plurality of at least three bearing support elements secured to the turret frame and extending therefrom toward the bearing ring,

a bearing mounted on the end of each bearing support element directed toward the bearing ring, all of the bearings being in equal bearing engagement with the bearing ring with the turret frame exactly centered on the selected azimuth axis, and

drive means for driving the turret to rotatively adjusted position about the azimuth axis.

2. An antenna support structure as defined in claim 1 wherein the turret frame is triangular, its three angles are spaced equally from the selected azimuth axis, and one of the bearing support elements is mounted at each of the three angles of the frame.

3. An antenna support structure as defined in claim 1 wherein the annular track has an exposed flange portion, and a holddown roller assembly is mounted on the turret frame, said holddown roller assembly comprising a holddown roller frame fixedly secured to the turret frame, a rocker beam mounted on the holddown roller frame for rocking movement in a radial plane from the selected azimuth axis and for pivotal adjustment about an upright axis, a roller journaled on the rocker beam for rolling engagement with the underside of the exposed flange portion of the track, and thrust means acting between the holddown roller frame and the rocker beam for urging the roller upwardly into preloaded pressure engagement with the underside of the exposed track flange portion.

4. An antenna support structure as claimed in claim 3 wherein the rocker beam is supported for rocking movement in a clevis mounted on the lower end of an upright threaded stud passing through a hole provided in the holddown roller support frame, and a nut screwed onto the stud provides adjustable support for the rocker beam for adjusting the holddown roller into full, tangent, preloaded relation with the exposed track flange portion.

5. An antenna support structure as claimed in claim 4 wherein a yoke secured to the holddown roller frame spans the rocker beam in spaced relation to its upright threaded support stud, and screw means mounted in each side of the yoke is adjusted to position the axis of the holddown roller along a radial plane from the selected azimuth axis.

6. An antenna support structure as claimed in claim 1 wherein the bearing ring is offset radially inwardly from the annular track and the exposed edge portion of the track is the radially inward edge portion thereof.

7. An antenna support structure as claimed in claim 6 wherein each bearing support element is an arm extending radially inwardly toward the bearing ring, and a bearing pad unit is mounted on the inner end of each bearing support arm and in bearing, turret-centering engagement with the bearing ring.

8. An antenna support structure as claimed in claim 7 wherein each bearing pad unit comprises a base portion on the radially inward end of one of the bearing support arms, a bearing pad mount has swivel support on each bearing pad base portion, and a bearing pad is interposed between each bearing pad mount and the bearing ring for bearing engagement with the bearing ring, each of the bearing pads having equal, adjusted, pressure engagement with the bearing ring with the turret frame exactly centered on the selected azimuth axis.

9. An antenna support structure as claimed in claim 8 wherein the adjusted pressure engagement of each bearing pad with the bearing ring is provided by threaded means acting between the inner end of each bearing support arm and the base portion of the bearing pad unit mounted thereon.

. 10. An antenna support structure as claimed in claim 9 wherein the height of each bearing pad unit is less than the distance between the inner end of each arm and the bearing ring, and a space between the base of each bearing pad unit and he inner end of the bearing support arm upon which said each bearing pad is mounted is filled with a hard bedding material.

11. An antenna support structure as claimed in claim 1 wherein the base has an annular, steplike seat formed therein with its axis substantially coincident with the selected azimuth axis, said seat having a horizontal portion and a vertical riser portion, a plurality of axially upright threaded bearing ring support members embedded in the horizontal portion of the seat with threaded end portions thereof projecting upwardly through oversize holes provided therefor in the bearing ring, a nut screwed onto each projecting threaded portion and in adjusted, supporting relation with the bearing ring, and means for exerting force between selected points circumferentially of the bearing ring and the vertical riser portion of the seat for positioning the bearing ring with its axis exactly coincident with the selected azimuth axis.

12. An antenna support as claimed in claim 11 wherein the bearing ring has a plurality of threaded holes therein at spaced intervals throughout the circumference thereof with the axis of each threaded hole directed toward the riser portion, and each said force-exerting means is a screw. screwed into one of said threaded holes and in endwise bearing engagement with said riser portion.

t I I t 

1. An antenna support structure comprising, a base having a selected azimuth axis, an annular turret support track mounted in leveled condition on the base with its axis substantially coincident with the selected azimuth axis, a bearing ring of different diameter from the track mounted on the base substantially coaxially with, and in radially spaced relation to the track, means for adjusting the bearing ring to bring its axis into exact coincidence with the selected azimuth axis, an antenna support turret mounted for rotative adjustment on the track, said turret comprising a turret frame mounted substantially coaxially with the track, a plurality of at least three turret support wheels mounted on the turret frame and riding circumferentially along the annular track, a plurality of at least three bearing support elements secured to the turret frame and extending therefrom toward the bearing ring, a bearing mounted on the end of each bearing support element directed toward the bearing ring, all of the bearings being in equal bearing engagement with the bearing ring with the turret frame exactly centered on the selected azimuth axis, and drive means for driving the turret to rotatively adjusted position about the azimuth axis.
 2. An antenna support structure as defined in claim 1 wherein the turret frame is triangular, its three angles are spaced equally from the selected azimuth axis, and one of the bearing support elements is mounted at each of the three angles of the frame.
 3. An antenna support structure as defined in claim 1 wherein the annular track has an exposed flange portion, and a holddown roller assembly is mounted on the turret frame, said holddown roller assembly comprising a hold down roller frame fixedly secured to the turret frame, a rocker beam mounted on the holddown roller frame for rocking movement in a radial plane from the selected azimuth axis and for pivotal adjustment about an upright axis, a roller journaled on the rocker beam for rolling engagement with the underside of the exposed flange portion of the track, and thrust means acting between the holddown roller frame and the rocker beam for urging the roller upwardly into preloaded pressure engagement with the underside of the exposed track flange portion.
 4. An antenna support structure as claimed in claim 3 wherein the rocker beam is supported for rocking movement in a clevis mounted on the lower end of an upright threaded stud passing through a hole provided in the holddown roller support frame, and a nut screwed onto the stud provides adjustable support for the rocker beam for adjusting the holddown roller into full, tangent, preloaded relation with the exposed track flange portion.
 5. An antenna support structure as claimed in claim 4 wherein a yoke secured to the holddown roller frame spans the rocker beam in spaced relation to its upright threaded support stud, and screw means mounted in each side of the yoke is adjusted to position the axis of the holddown roller along a radial plane from the selected azimuth axis.
 6. An antenna support structure as claimed in claim 1 wherein the bearing ring is offset radially inwardly from the annular track and the exposed edge portion of the track is the radially inward edge portion thereof.
 7. An antenna support structure as claimed in claim 6 wherein each bearing support element is an arm extending radially inwardly toward the bearing ring, and a bearing pad unit is mounted on the inner end of each bearing support arm and in bearing, turret-centering engagement with the bearing ring.
 8. An antenna support structure as claimed in claim 7 wherein each bearing pad unit comprises a base portion on the radially inward end of one of the bearing support arms, a bearing pad mount has swivel support on each bearing pad base portion, and a bearing pad is interposed between each bearing pad mount and the bearing ring for bearing engagement with the bearing ring, each of the bearing pads having equal, adjusted, pressure engagement with the bearing ring with the turret frame exactly centered on the selected azimuth axis.
 9. An antenna support structure as claimed in claim 8 wherein the adjusted pressure engagement of each bearing pad with the bearing ring is provided by threaded means acting between the inner end of each bearing support arm and the base portion of the bearing pad unit mounted thereon.
 10. An antenna support structure as claimed in claim 9 wherein the height of each bearing pad unit is less than the distance between the inner end of each arm and the bearing ring, and a space between the base of each bearing pad unit and the inner end of the bearing support arm upon which said each bearing pad is mounted is filled with a hard bedding material.
 11. An antenna support structure as claimed in claim 1 wherein the base has an annular, steplike seat formed therein with its axis substantially coincident with the selected azimuth axis, said seat having a horizontal portion and a vertical riser portion, a plurality of axially upright threaded bearing ring support members embedded in the horizontal portion of the seat with threaded end portions thereof projecting upwardly through oversize holes provided therefor in the bearing ring, a nut screwed onto each projecting threaded portion and in adjusted, supporting relation with the bearing ring, and means for exerting force between selected points circumferentially of the bearing ring and the vertical riser portion of the seat for positioning the bearing ring with its axis exactly coincident with the selected azimuth axis.
 12. An antenna support as claimed in claim 11 wherein the bearing ring has a plurality of threaded holes therein at spaced intervals throughout the circumference thereof with the axis of each threaded hole directed toward the riser portion, and each said force-exerting means is a screw, screwed into one of said threaded holes and in endwise bearing engagement with said riser portion. 